Electrical relay



May 19, 1942. R. M. LAURENYsoN 2,283,270

v ELECTRICAL RELAY Filed Nov. 9, 1940 HIS ATToRNr-:Y

Patented May 19, 1942 ELECTRICAL RELAY Robert M. Laurenson, Forest Hills, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a. corporation of Pennsylvania Application November 9, 1940, Serial No. 365,039

4- Claims.

My invention relates to electrical relays, and particularly to electrical relays of the biased polar type. More particularly, my present invention relates to biased polar relays which are particularly suitable for, although in no way limited to, use in centralized trame controlling systems for railroads, such for example, as that disclosed and claimed in an application for Letters Patent of the United States, Serial No. 223,287, filed by Clarence S. Snavely, and Alfred B. Miller, on August 5, 1938u for Remote control systems.

In a system of the type referred to a biased polar relay is required for the line circuits having the characteristics of fast action, low energy consumption, and a high ratio of release'to pick up. These characteristics are necessary to permit fast operation of the system and to minimize the required line voltage while maintaining a high Value of release current, thus permitting operation of the system through adverse leakage conditions.

One .object vof my present invention is to provide a relay having the required characteristics.

Another object of my invention is to provide a relay which is highly sensitive and at the same time is stable in operation.

According to my invention, an armature comprising part of a centrally pivoted dynamically balanced rocker has its opposite ends disposed between and cooperating with pole faces formed by the confronting ends of two U-shaped magnetizable yokes which are constantly supplied with fiux preferably by a permanent magnet. The armature is surrounded by an energizing winding, and is provided with core pins of unequal lengths so arranged that the armature is free to swing closer to one set of pole faces than to the other. The rocker carries a plurality of exible contact fingers each of which cooperates only with a single fixed contact member mounted in a suitable frame which pivotally supports the rocker. The fingers are so adjusted that when the armature is in its mid Lstroke position, the contacts formed by the flexible contact fingers and xed contact members Will all be made but will exert substantially no load on the rocker, and the parts are so proportioned that the flux which is constantly supplied to the yokes will be sufficient when the relay Winding is deenergized to move the armature toward said one set of pole faces to the position in which the cooperating core pins engage such pole faces, whereby when said winding becomes energized, the energy required to swing the armature toward the other set `of pole faces will be a minimum and the relay will have a high ratio of pickup to release current.

Other objects and characteristics of my invention will become apparent as the description proceeds.

The relay forming the subject matter of my present invention is an improvement upon the relay described and claimed in Letters Patent of the United States No. 2,140,604, granted to Clarence S. Snavely, on December 20, 1938, for Electrical relays.

I shall describe one form of relay embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a front elevational view showing one form of relay embodying my invention, the front and rear cover plates of the relay being removed to better illustrate the construction of the operating parts. Fig. 2 is a sectional view taken substantially on the line II-II of Fig. 1. Figs. 3 to 6, inclusive, are diagrammatic views illustrating the operating characteristics of relays embodying my invention.

Similar reference characters refer to similar parts in each of the several views.

Referring to the drawing, the relay in the form here shown comprises a rectangular frame I of insulating material that can be readily moulded, such for example as a phenol condensation product, which frame supports all of the operating parts of the relay. Mounted on one side of the frame I are two U-shaped yokes 2 and 3 of magnetizable material. 'I'hese yokes are disposed with their upper and lower legs in spaced parallel confronting relation to provide pole faces 2a, 3a, 2b and 3b, and are constantly magnetized by a pair of permanent magnets only one of which 4 is visible in the drawing.

The relay also comprises an armature 5 of magnetizable material such as silicon steel moulded into an insulating rocker 6 adjacent the rear end thereof. The rocker 6 is pivotally mounted on front and rear pivots 'l and 8 secured respectively to front and rear pivot supports 9 and I0, which pivot supports, in turn, are secured to the frame l in the manner described and claimed in an application for Letters Patent of the United States, Serial No. 317,577, filed by Clarence S. Snavely, on February 6, 1940, for Electrical relays, which application became Patent No. 2,256,653 on September 23, 1941. The upper and lower ends of the armature 5 extend between and cooperate with the pole faces 2a3a., 2531i of the yokes 2 and 3 in such manner that the armature is free to swing between a normal extreme position in which a core pin a secured to the upper end of the armature engages the pole face 2a and a core pin 5b secured to the lower end of the armature engages the pole face 3b, and a reverse extreme position in which a core pin 5c secured to the upper end of the armature opposite the core pin 5a engages the pole face 3a and a core pin 5d secured to the lower end of the armature opposite the core pin 5b engages the pole face 2b. According to my present invention, the core pins 5a and 5b are made shorter than the core pins 5c and 5d, whereby the armature 5 is free to swing closer to the pole faces 2a and 3b than to the pole faces 2b and 3a.. The reasons for this construction of the core pins will be made clear as the description proceeds.

The operating winding of the relay comprises two coils II and I2 which surround the upper and lower ends of the armature with sufficient clearance to permit the necessary rocking movement thereof. The coil I I is connected by means of leads IIa and IIb to coil connectors I3a and I3b moulded into the opposite sides of the frame I, and the coil I2 is similarly connected by means of leads I2a and I2b to coil connectors Illa and I4b which are likewise moulded into the opposite sides of the frame I.

The insulating rocker 6 is provided at its forward end with four flexible contact fingers I5, I5, I'I and I8. These contact lingers extend radially toward the four corners of a rectangle, and cooperate respectively with a fixed reverse contact member I5a, a fixed normal contact member Ilia, a fixed reverse contact member I'Ia and a fixed normal contact member IBa, al1 of which fixed Contact members are moulded into the sides of the frame I. The front and back contact members are each provided at their inner ends with a portion which is bent at an angle to the main part of the contact member in such manner that when the armature 5 is midway between the two extreme positions determined by the core pins 5a, 5b, 5c and 5d, the bent portion of each contact member will extend parallel to the associated finger, and each bent portion is provided with a pair of Contact buttons 20 which cooperate with similar contact buttons 2I provided on the associated flexible contact finger to form a low resistance contact. The fixed contact members are so adjusted that when the armature occupies its mid stroke position, the contact buttons 2D on each finger will just touch the contact buttons 2| on the associated flexible contact iinger, and it will be apparent therefore that when the armature occupies its mid stroke position, both the normal and the reverse contacts will be closed, but that, when the armature is swung to the normal position, the normal contacts only will be closed, and that, when the armature is swung to its reverse position, the reverse contacts only will be closed. The reasons for this adjustment will be made clear presently.

External electrical connections with the flexible contact fingers are made by means of flexible fiat spring connector members 25, 26, 21 and 28 which are secured at one end to the fingers I5, IB, Il and I8, respectively, by means of the contact button 2| and at the other end to circuit connectors 25a, 26a, 21a and 28a, respectively, moulded into the frame I above and below, as the case may be, the coil connectors I3b, I3a, I4a and I4b. The spring connector members are bent into a substantially U-shape, and are so arranged that the net force exerted on the rocker by these members is substantially zero. This arrangement of the connector members forms no part of my present invention, and is described in the aforesaid mentioned application for Letters Patent of the United States, Serial No. 317,577, iiled by Clarence S. Snavely, on February 6, 1940, for Electrical relays.

With the relay constructed in the manner described it will be apparent that the contact iingers of the relay exert a force on the rocker which urges it toward its mid stroke position. It will also be apparent that when the rocker is in vits mid stroke position, the armature 5 will be closer to the pole faces 2a and 3b than it is to the pole faces 2b and 3a, with the result that in this position of the rocker the permanent magnet flux traversing the armature will exert a force on the armature which urges the rocker in a counterclockwise direction, as viewed in Fig. 1. It follows, therefore, that when the winding II--I2 is deenergized, the resultant force on the armature due to the contact springs and the permanent magnet is always in a counterclockwise direction. According to my invention the strength of the magnet, lengths of air gaps, and cross sectional area of the armature are so chosen with respect tothe force due to the contacts that when the winding II-I2 is deenergized, the resultant torque exerted on the armature will be sufficient to move the armature to the position in which the core pins 5a and 5b engage the pole faces 2a and 3b thus causing the armature to normally assume the position in which the normal contacts IG-IBa and I8-I8a are closed and the reverse contacts I5-I5a. and I1-IIa are open. That is to say, the parts are so proportioned that the spread between magnetic and mechanical centers, that is, the difference in length between the front core pins 5a5b and the back core pins 5c5d is such that the mechanical load curve and the permanent magnet curve never cross. This is illustrated graphically in Fig. 3.

Referring to Fig. 3, the abscissae represents the displacement of the armature while the ordinates represent the forces applied to the armature. The horizontal line AD represents the effective distance between the normal and reverse pole faces, the line A-B the length 1of the normal core pins 5a5b, the line CD the length of the reverse core pins 5c5d, and the line BC the stroke .of the armature. Curve PM represents the force acting on the armature by the permanent magnet alone, and curve SF represents the force acting on the armature by the contact fingers acting alone. It should be noted that the curve SF is plotted upside down with relation to the curve PM from the way in which the forces react in the relay. That is, the distance CJ: represents the permanent magnet force acting in a clockwise direction, while the distance Cy represents the contact spring force acting in a counterclockwise direction. This is done to more 4clearly show the exact relation in magnitude between the forces. It will be seen from an inspection of the curves PM and SF that*l the magnetic center of curve PM lies at point O which is midway between the normal and reverse pole faces while the mechanical center of the curve SF lies at point OI which is to the left of point O. In other words, the curve SF lies entirely to the left of the curve PM, and the force due to the contact fingers is offset from that due to the permanent magnet by an amount equal to the distance between O and OI. This offset is due to the fact that the core pins Salio .are `shorter than the vcore pins c5d. It should also be noted that Whatever the position of the armature between its normal and reverse position, if the winding II--I2 is then deenergized, the resultant force on the armature such as the difference between Cy and Cm, for example, is always in a counterclockwise direction. The energy which must be supplied to the windings I I-I2 to overcome this resultant force is represented by the shaded area between the curves. This energy consumption can be reduced to any degree which is practical to manufacture by reducing the spread between O and OI. The limit to which the energy can be reduced depends upon the minimum margin of permanent magnet pull over contact load which is necessary to provide the desired stability of operation.

Several other types of contact combinations all of which have the same biased polar characteristics without any mechanical bias other than that due to the contact fingers themselves are shown in Figs. 4, 5 and 6. Referring to these figures, Fig. 4 illustrates a contact combination in which both the normal and reverse contacts of the relay are open in an intermediate position of the armature, Fig. 5 illustrates a contact combination in which the reverse contact load is less than the normal contact load, while Fig. 6 illustrates a contact combination in which both the reverse and normal contacts remain closed for an intermediate portion of the stroke of the armature.

One advantage of a biased polar relay embodying my invention is that it will respond to current of one polarity only.

Another advantage of a biased polar relay embodying my invention is that the work done by the relay is only the useful work necessary to operate the contacts, and this work is not increased by a separate biasing element of any kind, which makes it possible to build the magnetic circle just large enough to do the necessary useful work. y

Another advantage of a relay constructed in accordance with my invention is that the armature section is minimized, which minimizes the residual and inertia forces, and hence makes possible fast action and a high release current.

A further advantage of a relay constructed in accordance with my invention is that this type of construction lends itself to close matching between spring and permanent magnet forces with resultant low energy consumption. At the same time, this matching can be modified to vary one characteristic more or less independently of the others.

A further advantage of a relay constructed in accordance with my invention is that, since the magnetic circuit needs to be only large enough to do the useful contact work, an economy of materials is effected in all parts. Moreover, the absence of any biasing means other than the contact fingers makes fewer parts to assemble and adjust in constructing the relay which tends to reduce the cost of the relay.

Although I have herein shown and described only a few forms of relays embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope .of my invention.

Having thus described my invention, what I claim is:

1. A relay comprising two magnetizable yokes `provided with confronting pole faces, an arma'- ture'pivotally supported intermediate its ends Vand having its endsl disposed between said pole faces, means for constantly supplying flux to said yokes for polarizing said armature, means for limiting the movement of said armature toward one set of pole faces to a smaller air gap than its movement toward the other set, a winding surrounding said armature, and contacts operatively connected with said armature and bias- !ing said armature to a position in which the resultant torque on said armature due to said contacts and to said permanent magnet when said winding is deenergized is always in the direction to move said armature toward said one set of pole faces.

2. A relay comprising two magnetizable yokes provided with confronting pole faces, an armature pivotally supported intermediate its ends and having its ends disposed between and cooperating with said pole faces, said armature being movable between normal and reverse positions, a permanent magnet connected with said yokes for polarizing said armature, normal and reverse contacts operatively connected with said armature and closed according as said armature occupies its normal or its reverse position, and a winding surrounding said armature, said fingers being so adjusted and the parts being so proportioned that the resultant torque ,on said armature due to said fingers and said permanent magnet when said winding is deenergized is always in the direction and is of sufficient magnitude to move said armature to its normal position, whereby said relay will respond to current of one polarity only.

3. A relay comprising two U-shaped yokes of magnetizable material mounted with their legs in spaced confronting relation to form pole faces, a centrally pivoted dynamically balanced rocker including an armature having its Yends disposed between and cooperating with the confronting pole faces of said yokes, said rocker also being provided with a plurality of radially extending flexible contact ngers, core pins secured to said armature and limiting the movement of the armature toward one set of pole faces to a smaller air gap than its movement toward the other set of pole faces, a single fixed contact member cooperating with each contact finger and so adjusted that in the mid stroke position of the armature each finger will just engage the associated fixed contact member, a winding surrounding said armature and effective when energized to supply flux to said armature, and a permanent magnet supplying fiux to said yokes and yof such strength that when said winding is deenergized the resultant torque exerted on the armature due to said magnet and said finger will be sufficient to move the armature to the position in which said core pins engage the pole faces of said one set.

4. A relay comprising two U-shaped yokes of magnetizable material mounted with their legs in spaced confronting relation to form pole faces, a centrally pivoted dynamically balanced rocker including an armature having its ends disposed between and cooperating with the confronting pole faces of said yokes, said rocker also being provided with a plurality of fiexible Contact fingers extending radially toward the four corners of a rectangle, core pins secured to said armature and limiting the movement of the armature toward one set of pole faces to a smaller air gap than its movement toward the other set of pole faces, a single xed contact member cooperating with each contact finger and so adjusted that in the mid stroke position of the armature each ringer will just engage the associated xed contact member but that in one extreme position of the armature two of the diametricaiiy opposite ngers will be out of engagement with the associated fixed Contact members and that in the other extreme position of the armature the remaining two diametricaliy opposite fingers Will be out of engagement With the associated fixed Contact members, whereby one set of contacts will be closed in one extreme position of the armature and the other set in the other extreme position of the armature, a winding surrounding said armature and effective when energized to supply flux to said armature, and a permanent magnet supplying flux to said yokes and of such strength that when said Winding is deenergized the resultant torque exerted on the armature due to said magnet and said fingers Will be sufcient to move the armature to the position in which said core pins engage the pole faces of said one set.

ROBERT M. LAURENSON. 

